1. Field of Invention
The present invention relates to through-wall flashing systems and fire prevention. More particularly, the present invention relates to flashing systems and methods of installing flashing systems at fenestrations in cavity wall construction.
2. Description of the Related Art
FIG. 1 illustrates a perspective view of a portion of a traditional masonry veneer wall 10. Traditionally, masonry wall 10 is constructed having a back-up wall or inner wythe 12 and an outer wythe 14. Inner wythe 12 is typically made of concrete masonry block 16, brick, wood, or steel frame construction elements. Outer wythe 14 is typically made of brick 18, stone, concrete block, stucco, or other cladding products. The inner and outer wythes 12, 14 are separated by a cavity 20. The width of cavity 20 can be specified by building code or architectural design preference, but is commonly dimensioned up to about six inches. Cavity 20 allows for up to four inches of outbound insulation 29 and about two inches of an air gap 28 between face 29a of outbound insulation 29 and inner face 14a of outer wythe 14 (or between outer face 12a of inner wythe and inner face 14a of outer wythe 14.)
The primary purpose of a masonry wall 10 constructed with a cavity 20 is to establish a capillary break and drainage plane between the outer face 12a of the inner wythe 12a and the inner face of outer wythe 14a. The break provides an inbound drainage plane, which prevents moisture from transferring from the inner face 14a of the outer wythe 14a to the outer face 12a of the inner wythe 12, whether the moisture is due to condensation formed on the inner face 14a or to water leaking through the outer wythe 14 to the inner face 14a of the outer wythe 14. The cavity 20 also helps reduce heat transfer by providing a blanket of air between wythes 12, 14. Water that penetrates the outer wythe 14 or that condenses on the inner face 14a of the outer wythe 14 will run down the inner face of 14a of the outer wythe 14 to a point where the downward flow 19 is redirected by the horizontal plane of the through-wall flashing membrane 22 located at and along the head of a fenestration a steel lintel 21. Moisture then continues to travel outward through weeps (not shown) embedded in the outer wythe 14. Water that condenses on the outer face 12a face of the inner wall 12a will drain downward onto the through-wall flashing membrane 22 and outward through the weeps by way of a weep device. The weep device can be a metal or plastic tube, a rope, or other device that extends horizontally through the outer wythe 14.
A through-wall flashing membrane 22 is one form of above-grade waterproofing that protects inner surfaces 12a, 14a of a masonry wall 10 from water intrusion. For water that forms in or enters the cavity 20, the through-wall flashing membrane 22 also directs this water out of masonry wall 10. Flashing is mandated in the International Building Code Section 1405.4, which states, “flashing shall be installed in such a manner so as to prevent moisture from entering the wall or to redirect it to the exterior.” Failure to comply with this code exposes the structural and interior wall components to water and associative rot, threatens indoor air quality, and reduces energy efficiency.
Traditional through-wall flashing membrane 22 is made of a continuously-formed, fitted, and sealed metal material (copper, stainless steel, or lead) or a continuously-formed, fitted, and sealed adhered or loose-laid waterproof membrane, all of which should be sloped to drain. To prevent delamination of a sealed joint, adhered and loose-laid membranes require full structural support to avoid sagging across gaps. Repairing failed joints is expensive.
To direct water out of the wall 10, metal through-wall flashing 22 is affixed to outer face of inner wythe 12 by any of several methods. One method is to insert an edge of flashing into a horizontal joint of the inner wythe 12, such as when the inner wythe 12 is made of masonry blocks. Another method is to insert the edge of the through-wall flashing 22 into a reglet, which is a horizontal slot or groove in an inner wythe made of poured concrete. Yet another method is to mechanically fasten the flashing to a cavity face 12a of the inner wythe 12 using screws and a termination bar 24. A termination bar 24 is a strip of metal or plastic with evenly-spaced screw holes and is designed to spread the load of through-wall flashing 22 evenly across the width of the bar. A termination bar may be used on any kind of inner wythe 12.
The through-wall flashing 22 runs down the cavity face 12a of inner wythe 12 to a horizontal ledge or shelf (e.g., horizontal leg 21b of lintel 21) or a wall foundation (not shown). Through-wall flashing 22 then turns and runs horizontally out of the wall 10 by extending through a mortar joint in the outer wythe 14, thereby providing a continuous path 19 that guides water horizontally through outer wythe 14. One such mortar joint is between lintel 21 and the row of bricks 18 installed on the lintel 21. Through-wall flashing 22 forms a continuous sheet that guides water to the outside surface 14a of outer wythe 14 and prevents water from reaching the interior of the building.
At a fenestration 30 (e.g., an opening for a door, window, louver, vents, etc.), an L-shaped lintel 21 extends across the opening and is supported by masonry members 18 (e.g., bricks) on either side of fenestration 30. Masonry members 18 above the opening are supported on the lintel 21. For an outer wythe 14 made of brick, lintel 21 is typically made of steel and has a vertical leg 21a with a height of about 3.5 inches and a horizontal leg 21b with a width of about 4.5 inches. Since lintel 21 is dimensioned to support bricks 18, a gap 28 remains between the inner wall 12 and the outer wall 14 at a top edge of fenestration 30. To close this gap 28 so that it is not visible, a piece of wood or polystyrene insulation may be installed between the inner wythe 12 and vertical leg 21a of the lintel 21 with the wood or metal header trim 36 extending across the gap 28. It is not uncommon to fill the air gap 28 along the header with spray foam or polystyrene insulation.
Since the water travels horizontally when the through-wall flashing 22 meets the lintel 21 or other ledge, an end dam 25 is commonly used to prevent moisture from traveling across the through-wall flashing 22 and into the wall 10. An end dam 25 also prevents moisture from entering the air cavity 20 when the through-wall flashing 22 is flat or has a slight upward slope towards the outside of the outer wall 14, a condition that may result in pooling. To further direct water away from outer wythe 14, a drip edge 26 may be installed across the horizontal leg 21b of the lintel 21, where the drip edge 26 extends beyond the outside surface 14a of outer wythe 14. Another option for closing the gap 28 between the inner and outer wythes along fenestration 30 is to select lintel 21 having a wider horizontal leg 21b so that vertical leg 21a abuts the insulation 29 on inner wythe 12 and horizontal leg 21b extends to cavity face 12a of inner wythe 12. A variation on this option is a lintel 21 having a rearwardly-extending leg (not shown) that extends from vertical leg 21a to inner wythe 12, thereby at least partially closing gap 28.
Through-wall masonry flashing 22 traditionally is made of heavy gauge copper or lead sheet that requires trained metal workers to install it correctly. Laps and seams need to be soldered, which is difficult to do properly in a watertight fashion.